1. Field of the Invention
The present invention relates to a semiconductor integrated circuit and a method of manufacturing same. More particularly, the present invention relates to a structure of a semiconductor integrated circuit and a method of manufacturing same in which coming off of the layer where the contacts are formed and the insulating film and breakage of the LSI can be prevented by reducing the number of contact holes.
2. Prior Art
Presently, in designing a semiconductor integrated circuit, when a wiring layer is changed in routing, contacts are regularly formed in numbers that can be formed, between wiring regions where different wirings overlap with each other, with the height, the width and the spacing determined by the design rule of each process, so as to be aligned in the direction of the height and the width of the contacts.
The above-mentioned height determined by the design rule of each process is the vertical size of rectangular contacts. Likewise, the width is the horizontal size of rectangular contacts. In the following description, “determined by the design rule of each process” is abbreviated as “determined by the process.”
When two or more wiring layers are changed, contacts of the intermediate layers are regularly formed in numbers that can be formed, with the height, the width and the spacing determined by the process in the same region as the region where the wirings of the upper and the lower layers overlap with each other.
A contact array comprises a plurality of contacts having a predetermined size and regularly arranged two-dimensionally, that is, arranged in a matrix at predetermined spacings. For example, a method has been proposed of preventing design rule errors caused by contact arrays of the above-described structure adjoining each other when wirings of different layers are connected together with an automatic layout apparatus (Japanese Laid-Open Patent Application No. 2000-284536 [page 1, FIG. 2]).
As described above, generally, in a contact array, when wirings are changed, contacts are regularly formed in numbers that can be formed, with the height, the width and the spacing determined by the process in the same region as a region where different wirings overlap with each other.
Moreover, as the process has been becoming finer in recent years, the area of each contact has been decreasing and the spacing between contacts has also been decreasing. For this reason, as shown in FIG. 13, in a case where the wiring layer is changed from a vertical wiring 1301 to a horizontal wiring 1302, when as many contacts as possible are regularly formed with the height, the width and the spacing determined by the process in a region where different wirings overlap with each other, the number of contacts making up a contact array 1303 increases. Consequently, there is a possibility that the number of contacts exceeds the number of contacts that can be formed in the unit area determined by the design rule of each process, for example, in a rectangular region of a predetermined size.
As shown in FIG. 13, when a large number of contacts are formed close to each other, there are cases where the layer where the contacts are formed and the insulating film come off and the LSI is broken. To prevent such coming off of the layer where the contacts are formed and the insulating film, it is effective to reduce the number of contacts formed in the region where the wiring layers overlap with each other.